As I've written before (President Obama is making a big mistake in Afghanistan.)
His commitment to send 30,000 more American troops will succeed only in more Americans coming home in coffins.
I will say that in October 2001 when the Afghan was began, I was fully in support of the mission. And I was among those who argued in 2002 (and since then as well) that it was a mistake to not finish the job in Afghanistan and instead be detoured into a costly and time- and resource- consuming war in Iraq.
So why not go back and finish the job now? Well, for starters it's not the same job. Back then it was pretty clear that we were fighting the people who attacked New York City and their patrons. But by now things have become considerably more muddled and it's hard to know who the good guys are, or even if there are any good guys.
Once again we are stuck in the middle of a civil war, this time between a corrupt and despotic government and the previous government which was run by fanatics. This has strong ethnic, regional, religious and tribal overtones as well as blood feuds that go back to the beginning of time.
There are, as General McCrystal himself said, very few members of Al-Qaeda even in Afghanistan right now, so in effect we are fighting the Taliban. Yes, the Taliban are terrible masters, fundamentalists who stone women to death just for speaking to a man and who kill barbers who shave off beards. But the truth is there are many terrible masters in the world, ranging from some of our 'allies' in the arab world to the North Korean regime to Robert Mugabe to the Chinese leaders who the President was just hob-nobbing with a couple of weeks ago. The decision about whether to commit American forces should be made using one metric and one metric alone, which is what is in the best interest of the United States? And I don't see how fighting the Taliban (a local Afghan movement, which thanks to our bumbling intervention over the past several years spilled over the border into Pakistan) solves anything.
Further, there is a definite risk that we could lose. In Iraq it was relatively easy to seal most of the borders when we ran the 'surge' (though I still contend that the best we can claim in Iraq is a pyrrhic victory.) The only mountainous borders Iraq has are with Turkey in the north and parts of the border with Iran to the east. But the Kurds who control northern Iraq and the Shi'ite government of Iran which controls Iran are both hostile to the Sunni Wahabbi sect that Al-Qaeda subscribes to and so won't tolerate Sunni fighters seeking refuge (even from us) on their soil. In contrast, it is well known that the weak Pakistani government has little or no control over areas along the border and the terrain is such that it is virtually impossible to prevent the movement of fighters across the border. Unless we are willing to remain there indefinitely with enough troops to squelch the insurgents it's safe to say they will simply hang out in Pakistan until they outlast us. Remember the Soviet Union tried doing this with half a million troops, five times what we will have, and they also came up short. It's easy to say that the Soviet military was overrated (though doing so just points out the scare tactics we had to live through to justify enormous military budgets in the 1980's) but by the same token it seems that the Mujahedeen who fought them (the direct precursor to the Taliban) were underrated.
What about the argument that if we just let the Taliban take over they will invite AQ back in and we will be back to a pre-September 11 world, waiting for the next horrific terrorist act?
First, I'm not sure how having our army there prevents terrorist attacks from taking place (since AQ can just as easily plan them when they are in Pakistan, as it is believed their senior leadership is.) But beyond that, we have been successful in attacking AQ in Pakistan without a massive commitment of American troops, even in areas where the Pakistani army has little presence. We've done it through the collection of intelligence, predator drone and other kinds of missile strikes, special forces operations and covert operations. I have no problem with these kinds of things (and have advocated for them in the past--- there are after all bad people in the world and if you don't advocate for war then you have to have a workable alternative for dealing with people who simply want to kill you if you don't kill them first.)
Second, if the hangup is AQ, why not see if we can negotiate a deal with the Taliban in which we won't fight them if they don't let AQ back in? Why would they honor the deal? Because we'd pay them to, of course. What? throw money at them? Well, the war is costing us a heck of a lot to fight, and one thing we've learned in the middle east is that allies can be bought. AQ needs the cover of the Taliban (in both Afghanistan and Pakistan) to have a place to operate. Why not just deny them that? Yes, that's a radical idea but as far as I know it hasn't even been tried yet. Let's see what their price is before we massively escalate a war which may in the end be unwinnable.